In general, extracorporeal circuits for CO2 removal from blood allow the patient's blood to be drained in an extracorporeal circuit in order to be artificially oxygenated and decarboxylated by means of a gas exchanger, such as an oxygenator. In particular, in a veno-venous extracorporeal system, venous blood returning towards the right atrium of the heart is collected in the extracorporeal circuit, pumped into the oxygenator and from there it is then reintroduced into the venous system.
The most commonly used oxygenators are membrane oxygenators, in which blood and oxygen (or a mixture rich in oxygen) are caused o flow on opposite sides of a membrane. Therefore, these types of apparatuses act upon the quantity of CO2 dissolved in the blood, which actually turns out to be a limited portion of the total content of CO2. As a matter of fact, it is known that 90% of the CO2 transported in blood is available in the form of bicarbonate ions according to the chemical equilibrium (I) below.CO2+H2OH2CO3H++HCO3−  (I)
A solution to increase CO2 removal from blood by means of membrane oxygenators can be the one of acting upon the chemical equilibrium (I) by causing an increase in the percentage of gaseous CO2. In this way, by increasing the concentration of gaseous CO2 as the target of the removal operated by the oxygenator, total CO2 removal from blood is improved.
One of the ways to act upon the chemical equilibrium (I) in favour of gaseous CO2 is exogenous acidification. The aforesaid exogenous acidification is carried out by adding an acid substance to the extracorporeal circuit upstream of the oxygenator.
Said acidification, by turning bicarbonate ions into dissolved CO2, increases the transmembrane pCO2 gradient, thus increasing the transfer of CO2 through the membrane of the oxygenator. Exogenous acidification of blood ensures the removal of the equivalent of 50% of the total production of CO2 of an adult man from an extracorporeal blood equalling 250 ml/min.
As an alternative, a technique based on ventilation of acidified dialysate was developed, which proved to be slightly less efficient (10-15%) than direct ventilation of blood, but reduces the exogenous surface in contact with the blood and, therefore, can have possible advantages.
In both cases, the acidification is obtained through infusion of a concentrated solution of metabolizable organic acid, for example lactic acid. However, when they are infused in an exogenous manner, despite their high clearance, they can cause a certain level of metabolic acidosis and a slight increase in the total corporeal production of CO2.
Therefore, as a person skilled in the art can easily understand, this addition of acid can reduce the efficiency of the extracorporeal CO2 removal technique and can lead to a series of drawbacks, which must be handled without altering the patient's homeostasis.
ITBO20090437 describes an extracorporeal circulation system, in which the removal of CO2 and bicarbonates is operated by means of a device for the electrolysis of plasmatic water. However, this device uses pure water and, as a drawback, it does not allow current to properly circulate and, therefore, it cannot ensure an effective ion separation. Furthermore, the fact that one of electrodes is arranged in direct contact with plasmatic water causes the formation of gaseous chlorine, which is notoriously toxic, and the precipitation of calcium carbonates, which can cause pulmonary embolisms.